Correlating diffusion-weighted MRI intensity with type 2 pathology in mixed MM-type sporadic Creutzfeldt-Jakob disease

The existence of affected subjects with both abnormal prion protein (PrP^Sc) types has been reported, and their clinical features were somewhat similar to the dominant PrP^Sc type but varied in sporadic Creutzfeldt-Jakob disease (sCJD). Presently, the antemortem identification of both PrP^Sc types in sCJD is not possible. In this study, we attempted to clinically predict the concurrence of MM-type sCJD with another PrP^Sc type in the same individual. We retrospectively identified seven MM-type sCJD cases with both fine vacuole-type spongiform (FV) and large confluent vacuole-type spongiform change (LCV) among 49 sCJD cases. We reviewed clinical features, pathological findings, and radiological abnormalities in these seven cases. We also conducted a regional systemic study with five brains to associate the spongiform-change pattern with hyperintensity on magnetic resonance diffusion-weighted imaging (DWI) using the signal intensity index (SII). In the case series study, the one patient with dominant LCV showed longer disease duration, later onset of typical symptoms, no periodic sharp wave complexes in electroencephalography, and negative 14–3-3 protein findings compared to the six FV-dominant patients. LCV-dominant lesions tended to show higher intensity on DWI than did the FV-dominant lesions in respective patients. In the regional systemic study, LCV-dominant regions showed significantly higher SII on DWI than did the FV-dominant regions. In conclusion, mixed MM-type sCJD generally showed the clinical features of the phenotype that was dominant in pathological distribution. The SII may be clinically useful for investigating the concurrence of PrP^Sc type 2 in cases with the typical clinical course of MM1-type sCJD.